Electron beam exposure mask and electron beam exposure method using the same

ABSTRACT

An electron beam exposure mask which makes it possible to reduce the number of times of exchange and to shorten the exposure time, is disclosed. The electron beam exposure mask ( 10 ) comprises at least two each of one or at least two kinds of exposure regions, for example, three kinds of exposure regions consisting of hole layer exposure regions (A), wiring layer exposure regions (B), and gate layer exposure regions (C). By this, at the time of conducting exposure by use of each exposure region, it suffices to move the exposure region to a predetermined exposure position, and it is unnecessary to exchange the electron beam exposure mask ( 10 ) by taking it out of the electron beam exposure device. Further, since at least two each of each kind of exposure regions are provided, an exposure region stained during use can be substituted with another exposure region, so that the number of times of cleaning of the electron beam exposure mask ( 10 ) is reduced, and the number of times of exchange of the electron beam exposure mask ( 10 ) can be reduced. Therefore, the exposure time in a lithography step can be shortened.

TECHNICAL FIELD

The present invention relates to an electron beam exposure mask, andparticularly to an electron beam exposure mask provided with a pluralityof exposure regions in each of which an exposure pattern to betransferred to a wafer is formed.

BACKGROUND ART

At present, in the lithography technology for forming a semiconductorpattern on a wafer, the main stream is the system in which reductionexposure of an original of design pattern called a photomask onto awafer is conducted by use of light. The reduction ratio at the time ofthe reduction exposure is 1/5 or 1/4, and i rays (wavelength: 365 nm)and deep UV rays (wavelength: 248 nm, 193 nm) are used for the exposure.It is expected that an exposure wavelength of 157 nm will also beadopted for the exposure in the future. However, the size ofsemiconductor devices has been reduced at a speed higher than that ofthe advancement of such light lithography, and there is a request forputting a new lithography technology into practical use.

In recent years, as a lithography technology with a higher resolution,an electron beam projection exposure technology using an electron beamexposure device such as EPL (electron beam projection lithography) andLEEPL (low energy electron beam proximity projection lithography) hasbegun to be developed. The EPL is a technology in which an electron beamexposure mask which is four times as large as a design pattern is used,and exposure is conducted under a high acceleration voltage of 100 kV.In the LEEPL, on the other hand, the electron beam exposure mask isequal to the design pattern in size, and the acceleration voltage is aslow as about 2 kV.

In such an electron beam projection exposure as these, a stencil mask inwhich an exposure pattern to be transferred onto a wafer is bored in anelectron beam exposure mask substrate is used as the electron beamexposure mask.

FIGS. 4A to 4C are plan views showing examples of a transfer pattern andan electron beam exposure mask for forming the transfer pattern, inwhich FIG. 4A shows the transfer pattern, and FIGS. 4B and 4C showcomplementary masks.

In the case of transferring an annular pattern 100 as shown in FIG. 4Aonto a wafer by the electron beam projection exposure, a stencil maskhaving an opening portion in the same shape as the annular pattern 100cannot hold the central dot pattern 100 a in the stencil mask.Therefore, it is necessary to split the stencil mask into twocomplementary masks 101 and 102 complementary to each other, as shown inFIGS. 4B and 4C, and to conduct exposure by use of the complementarymasks 101 and 102, thereby forming the annular pattern 100 on the wafer.

Meanwhile, in the process of producing a semiconductor, there is thebasic process of forming each layer for forming semiconductor devices,forming a resist pattern by lithography, and conducting etching. In thelithography step, hitherto, a single electron beam exposure mask hasbeen provided only with an exposure region for forming a single layer inan individual step in production of a wafer; for example, an electronbeam exposure mask for a device separation layer has been provided onlywith an exposure region in which an exposure pattern for forming thedevice separation layer is formed, or an electron beam exposure mask fora gate layer has been provided only with an exposure region in which anexposure pattern for forming the gate layer is formed.

FIG. 5 is a plan view showing an example of a conventional electron beamexposure mask to be used in the lithography step.

The electron beam exposure mask 200 is provided with exposure patterns201 a, 201 b, 201 c, 201 d in an exposure region 201 thereof. The fourexposure patterns 201 a, 201 b, 201 c, 201 d may be different in patternshape, but, even in that case, all the exposure patterns are for formingthe same layer.

Namely, in the related art, it has been necessary to exchange theelectron beam exposure mask with an electron beam exposure mask providedwith an exposure region in which exposure patterns for forming a layerare formed, each time of forming each layer in an individual step in theproduction of a wafer, in the lithography step.

However, in an electron beam exposure device at present, the exposureatmosphere is a vacuum, unlike the case of light exposure, and,therefore, exchange of the electron beam exposure mask takes much time.

The exposure time in the case of the electron beam exposure deviceincludes electron beam irradiation time, electron beam conditioningtime, alignment time, electron beam exposure mask transport time, wafertransport time, etc.; thus, the electron beam exposure device takeslonger exposure time than in the case of the light exposure deviceswidely used hitherto, and the throughput is lower accordingly.Particularly, in the production of small amounts of many kinds ofdevices, the number of wafers to be exposed is small, and it isnecessary to frequently exchange the electron beam exposure maskaccording to the formation of each layer. Therefore, the exposure timeis prolonged by the exchange of the electron beam exposure mask, theposition measurement after setting the electron beam exposure mask, andthe like, which is a major cause of lowering of the throughput of thelithography step.

In the case of using complementary masks as the electron beam exposuremask, also, two electron beam exposure masks provided respectively withexposure patterns complementary to each other are used at the time oftransferring an exposure pattern onto a wafer, so that the electron beamexposure mask must be exchanged for forming the complementary patterns,and the exposure time is prolonged accordingly.

In addition, unlike a photomask, the electron beam exposure mask cannotbe used with a pellicle. Therefore, the useful life of the electron beamexposure mask may be shortened by adhesion thereto of dirt or foreignmatter, so that the electron beam exposure mask must be frequentlycleaned. In the case of cleaning the electron beam exposure mask, also,it is necessary to exchange the electron beam exposure mask, and theexposure time is prolonged accordingly.

The present invention has been made in consideration of theabove-mentioned problems. Accordingly, it is an object of the presentinvention to provide an electron beam exposure mask which makes itpossible to reduce the number of times of exchange thereof and toshorten the exposure time.

DISCLOSURE OF INVENTION

According to the present invention, there is provided an electron beamexposure mask comprising an exposure region in which an exposure patternto be transferred onto a wafer is formed, wherein the electron beamexposure mask comprises at least two each of one or at least two kindsof exposure regions.

According to the above constitution, the electron beam exposure maskcomprises at least two each of one or at least two kinds of exposureregions; therefore, at the time of exposure using each exposure region,it suffices to move the exposure region to a predetermined exposureposition, and it is unnecessary to exchange the electron beam exposuremask by bringing the electron beam exposure mask to the outside of anelectron beam exposure device. In addition, since the electron beamexposure mask comprises at least two exposure regions of one kind, whenone of the exposure regions is stained, another of the exposure regionscan be used in place of the stained exposure region, so that the numberof times of cleaning of the electron beam exposure mask is reduced.

In addition, according to the present invention, there is provided anelectron beam exposure mask comprising an exposure region in which anexposure pattern to be transferred onto a wafer is formed, wherein theelectron beam exposure mask comprises one exposure region in which oneexposure pattern is formed, and another exposure region in which anotherexposure pattern is formed.

According to the above constitution, the electron beam exposure maskcomprises one exposure region and another exposure region. Therefore,different exposure patterns, for example, complementary patterns ofwhich one exposure pattern and another exposure pattern arecomplementary to each other, can be exposed without taking the electronbeam exposure mask out of the electron beam exposure device, so that thenumber of times of exchange of the electron beam exposure mask isreduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of an electron beam exposure mask according to afirst mode for carrying out the present invention;

FIG. 2 is a plan view of an electron beam exposure mask according to asecond mode for carrying out the present invention;

FIG. 3 is a plan view of an electron beam exposure mask according to athird mode for carrying out the present invention;

FIGS. 4A to 4C are plan views showing examples of a transfer pattern andan electron beam exposure mask for forming the transfer pattern, inwhich FIG. 4A shows the transfer pattern, and FIGS. 4B and 4C showcomplementary masks; and

FIG. 5 is a plan view showing an example of a conventional electron beamexposure mask to be used in a lithography step.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, a mode for carrying out the present invention will be describedreferring to the drawings.

FIG. 1 is a plan view of an electron beam exposure mask according to afirst mode for carrying out the present invention.

The electron beam exposure mask 10 is provided with exposure regions inwhich exposure patterns to be transferred onto a wafer are formedrespectively, for example, three kinds of exposure regions consisting ofa hole layer exposure region A as an exposure region in which anexposure pattern to be transferred to a hole layer in the process ofproducing a semiconductor is formed, a wiring layer exposure region B asan exposure region in which an exposure pattern to be transferred to awiring layer is formed, and a gate layer exposure region C as anexposure region in which an exposure pattern to be transferred to a gatelayer is formed. Three each of these exposure regions are provided in asingle sheet of the electron beam exposure mask 10, namely, a total ofnine exposure regions are provided in the single sheet of the electronbeam exposure mask 10.

In the case of electron beam exposure by use of the electron beamexposure mask 10 constituted as above, normally, the three exposureregions consisting of the hole layer exposure region A, the wiring layerexposure region B and the gate layer exposure region C are used. Theremaining two each of the exposure regions are used as spare masks withwhich an exposure region stained during use is exchanged.

Here, a case in which ten wafers to be exposed are used, and theexposure pattern to be transferred to the hole layer is exposed onto thefirst to third wafers, the exposure pattern to be transferred to thewiring layer is exposed onto the fourth to sixth wafers, and theexposure pattern to be transferred to the gate layer is exposed onto theseventh to tenth wafers, will be described.

In this case, according to the electron beam exposure mask 10 accordingto the present mode, exposure onto the wafer can be continuouslyconducted without exchanging the electron beam exposure mask 10, ascontrasted to the related art method in which mask exchange is conductedat a time point after exposure onto the hole layer and before exposureonto the wiring layer and at a time point after exposure onto the wiringlayer and before exposure onto the gate layer. In the case of using theelectron beam exposure mask 10 according to the present mode, first,exposure onto the first to third wafers of the ten wafers to be exposedis conducted by use of the hole layer exposure region A. Next, a maskstage with the electron beam exposure mask 10 fixed thereon is moved tochange the positions of the hole layer exposure region A and the wiringlayer exposure region B, and exposure onto the fourth to sixth wafers isconducted by use of the wiring layer exposure region B. As for the gatelayer exposure region C, also, the mask stage with the electron beamexposure mask 10 fixed thereon is moved to change the positions of thewiring layer exposure region B and the gate layer exposure region C, andexposure onto the seventh to tenth wafers is conducted by use of thegate layer exposure region C.

Thus, according to the electron beam exposure mask 10 according to thepresent mode, in the case of conducting exposure onto a plurality ofkinds of layers, only the wafers are exchanged, and the electron beamexposure mask need not be exchanged by taking it out of the electronbeam exposure device, though each of the exposure regions is movedaccording to the exposure onto each of the layers. Therefore, it ispossible to shorten the exposure time.

The hole layer, the wiring layer, and the gate layer used in the abovedescription are mere examples; as the exposure regions formed in theelectron beam exposure mask 10, naturally, exposure regions in whichexposure patterns for other layers than the just-mentioned layers areformed may be adopted. In addition, the exposure pattern of the exposureregions formed in the electron beam exposure mask 10 may be of aplurality of kinds, such as the kinds for the hole layer, for the wiringlayer, and for the gate layer, and may be of a single kind, such as thekind for only the hole layer or for only the wiring layer. Furthermore,while the number of the spare masks are two in the above description,the number is not limited to this.

FIG. 2 is a plan view of an electron beam exposure mask according to asecond mode for carrying out the present invention.

The electron beam exposure mask 20 is provided with exposure regions inwhich exposure patterns to be transferred onto a wafer are formed, forexample, a total of nine exposure regions consisting of hole layerexposure regions A1, A2, A3 as exposure regions in which an exposurepattern to be transferred to a hole layer in the process of producing asemiconductor is formed, wiring layer exposure regions B1, B2, B3 asexposure regions in which an exposure pattern to be transferred to awiring layer is formed, and gate layer exposure regions C1, C2, C3 asexposure regions in which an exposure pattern to be transferred to awiring layer is formed. Here, same-shape exposure patterns which areexposure patterns of the same shape are formed in the hole layerexposure regions A1, A2, A3. Similarly, same-shape exposure patterns areformed in the wiring layer exposure regions B1, B2, B3, and same-shapeexposure patterns are formed in the gate layer exposure regions C1, C2,C3.

Electron beam exposure by use of the electron beam exposure mask 20constituted as above will be described by taking as an example the caseof forming a transfer pattern by double exposure.

First, in the case of exposing an exposure pattern to be transferred tothe hole layer, exposure is conducted with an exposure amount of ½ of atotal exposure amount necessary for forming the transfer pattern, by useof the hole layer exposure region A1. Next, a mask stage with theelectron beam exposure mask 20 fixed thereon is moved to move the holelayer exposure region A2 to the exposure position for the hole layer atwhich the hole layer exposure region A1 has been disposed. By use of thehole layer exposure region A2, exposure is conducted with an exposureamount of ½ of the total exposure amount necessary for forming thetransfer pattern.

Subsequently, in the case of exposing an exposure pattern to betransferred to the wiring layer, exposure is conducted with an exposureamount of ½ of a total exposure amount necessary for forming thetransfer pattern, by use of the wiring layer exposure region B1. Then,the mask stage is moved, and exposure is conducted with an exposureamount of ½ of the total exposure amount necessary for forming thetransfer pattern, by use of the wiring layer exposure region B2.

Also in the case of exposing an exposure pattern to be transferred tothe gate layer, similarly, exposure is conducted with an exposure amountof ½ of a total exposure amount necessary for forming the transferpattern, by use of the gate layer exposure region C1, then the maskstage is moved, and exposure is conducted with an exposure amount of ½of the total exposure amount necessary for forming the transfer pattern,by use of the gate layer exposure region C2.

In the case of double exposure as just-mentioned, the hole layerexposure region A3, the wiring layer exposure region B3, and the gatelayer exposure region C3 are used as spare masks with which an exposureregion stained during use is to be exchanged.

Besides, in the case of triple exposure by use of the electron beamexposure mask 20 according to the present mode, exposure using each ofthe hole layer exposure regions A1, A2, A3 is conducted with an exposureamount of ⅓ of a total exposure amount necessary for forming thetransfer pattern. Also as for the wiring layer exposure regions B1, B2,B3 and the gate layer exposure regions C1, C2, C3, similarly, exposurewith an exposure amount of ⅓ of the total exposure amount is conducted.

Thus, multiple exposure of a transfer pattern is conducted by use ofdifferent exposure regions of the same-shape exposure patterns, forexample, the hole layer exposure regions A1, A2, A3 formed in theelectron beam exposure mask 20. Therefore, it is unnecessary to exchangethe electron beam exposure mask 20 by taking it out of the electron beamexposure device, and the exposure time can be shortened. Further, thereis rarely the case where the same-shape exposure patterns have defectsat the same position, so that defect transfer property can be reduced bythe multiple exposure using the different exposure regions.

The hole layer, the wiring layer, and the gate layer used in the abovedescription are mere examples; as the exposure regions formed in theelectron beam exposure mask 20, naturally, exposure regions in whichexposure patterns for other layers than the just-mentioned layers areformed may be adopted. In addition, the exposure pattern of the exposureregions formed in the electron beam exposure mask 20 may be of aplurality of kinds, such as the kinds for the hole layer, for the wiringlayer, and for the gate layer, and may be of a single kind, such as thekind for only the hole layer or for only the wiring layer. Further,while the exposure regions are formed by setting the number of times ofexposure to be two or three in the above description, the number oftimes of exposure and the number of exposure regions formed are notlimited to these values.

FIG. 3 is a plan view of an electron beam exposure mask according to athird mode for carrying out the present invention.

The electron beam exposure mask 30 is provided with two each of exposureregions D1, D2 in which exposure patterns to be transferred onto a waferare formed respectively. The exposure pattern in the exposure region D1and the exposure pattern in the exposure region D2 are complementarypatterns which are complementary to each other, and a desired transferpattern can be obtained by exposure by use of both of the exposureregions D1, D2.

In the case of conducting electron beam exposure by use of such anelectron beam exposure mask 30 as this, first, exposure is conducted byuse of the exposure region D1, then a mask stage with the electron beamexposure mask 30 fixed thereon is moved to change the positions of theexposure region D1 and the exposure region D2, and exposure is conductedby use of the exposure region D2.

Thus, since the exposure regions D1, D2 in which the exposure patternscomplementary to each other are formed are formed in the single sheet ofelectron beam exposure mask 30, the complementary patterns can be formedwithout exchanging the electron beam exposure mask 30 with another oneby taking it out of the electron beam exposure device at the time ofexposure, and the exposure time can be shortened.

While two each of the exposure regions D1, D2 are provided, one set ofthe exposure regions D1, D2 are normally used for exposure, and theremaining two exposure regions D1, D2 can be used as spare masks forexchange upon staining of the one set of exposure regions D1, D2 beingused.

In addition, since two each of the exposure regions D1, D2 are provided,defect transfer property can be reduced by conducting multiple exposurewith an exposure amount of ½ of a total exposure amount necessary forforming a transfer pattern, by use of the exposure regions D1, D2,respectively.

While the case where two each of the exposure regions D1, D2 are formedin the electron beam exposure mask 30 has been described above, exposureregions in which other complementary patterns different in shape fromthe exposure regions D1, D2 are formed may be formed in the electronbeam exposure mask 30 in addition to the exposure regions D1, D2.Besides, while the electron beam exposure mask 30 described above isprovided with a total of four exposure regions, the number of exposureregions formed is not limited to this.

Furthermore, while the exposure patterns complementary to each other areformed respectively in the exposure regions D1, D2 in the abovedescription, exposure patterns to be transferred to layers such as, forexample, a hole layer, a wiring layer, and a gate layer, may be formedin the exposure regions D1, D2.

In the above description, in the case of conducting the exposure asequal-size exposure, the exposure patterns in the exposure regionsformed in the electron beam exposure mask are the same in size with thetransfer patterns formed on the wafer, so that a larger number ofexposure regions can be formed in the electron beam exposure mask, ascompared with the case of ¼-fold exposure or ⅕-fold exposure, wherebythe effect of shortening the exposure time is enhanced.

As has been described above, according to the present invention, atleast two each of one or at least two kinds of exposure regions areformed in a single sheet of electron beam exposure mask. By this, it ispossible to reduce the number of times of exchange of the electron beamexposure mask and to shorten the exposure time, in a lithography step.

In addition, where exposure patterns complementary to each other areformed in a single sheet of electron beam exposure mask, complementarypatterns can be formed without taking the electron beam exposure maskout of the electron beam exposure device, and the exposure time can beshortened.

By use of different exposure regions formed in a single sheet ofelectron beam exposure mask, it is possible to perform multiple exposurewithout taking the electron beam exposure mask out of the electron beamexposure device, to reduce the number of times of exchange of theelectron beam exposure mask, and to reduce defects in the transferredpattern.

Furthermore, since the number of times of cleaning of the electron beamexposure mask is reduced, the number of times of exchange of theelectron beam mask is reduced, and the time for the exchange can beomitted.

With the electron beam exposure mask as described above, it is possibleto reduce the number of sheets of the electron beam exposure masks usedfor exposure, and to contrive a reduction in cost and a reduction in thestorage area for the electron beam exposure masks.

1. An electron beam exposure mask comprising: a plurality of exposureregions each having an exposure pattern, wherein each exposure patternis to be transferred onto one of a plurality of multi-layer wafers,wherein each of a plurality of first exposure regions of the pluralityof exposure regions transfers a first exposure pattern to a first layerof each multi-layer wafer and each of a plurality of second exposureregions of the plurality of exposure regions transfers a second exposurepattern to a second layer of each multi-layer wafer.
 2. An electron beamexposure mask comprising: a plurality of exposure regions each having anexposure pattern to be transferred onto one of a plurality ofmulti-layer wafers, wherein a first exposure region of the plurality ofexposure regions transfers a first exposure pattern to a first layer ofeach multi-layer wafer and a second exposure region of the plurality ofexposure regions transfers a second exposure pattern to a second layerof each multi-layer wafer.
 3. The electron beam exposure mask as setforth in claim 2, wherein said first exposure pattern and said secondexposure pattern are complementary patterns.
 4. An electron beamexposure method by use of an electron beam exposure mask that includes afirst exposure region and a second exposure region in which a pluralityof exposure patterns to be transferred onto a plurality of multi-layerwafers is formed, said method comprising the steps of: transferring afirst pattern to a first layer of a first group of the plurality ofmulti-layer wafers by using the first exposure region of the exposuremask; and transferring a second pattern to a second layer of a secondgroup of the plurality of multi-layer wafers using the second exposureregion of the exposure mask.
 5. The electron beam exposure method as setforth in claim 4, further comprising the steps of: exposing the firstlayer of the first group of the plurality of multi-layer wafers by usinga third exposure region having a third exposure pattern that is of asame shape as the first exposure pattern of said first exposure region;and exposing the second layer of the second group of the plurality ofmulti-layer wafer using a fourth exposure region having a fourthexposure pattern that is of a same shape as the second exposure patternof said second exposure region.
 6. The electron beam exposure method asset forth in claim 4, wherein said first exposure pattern and saidsecond exposure pattern are complementary patterns.